[Info-vax] queue errors

[Bob Koehler]

In article <f322bd12-6167-44d1-8082-5498c6239596 at ib4g2000vbb.googlegroups.com>, Tom Adams <w.tom.adams at gmail.com> writes:
> 
> Prompted by your post, I studied and tested the /CHECK qualifier we
> use.  The only difference between it and /CHECK=3DALL is that we turn
> off runtime underflow checking. How is underflow checking a software
> quality issue, since one always has to guard against or divide by zero
> and other places were zero is a problem in calculations? (I am not
> asking a rhetorical question, I really would like to know if it is a
> quality issue.)

   Divide by zero, if not a specific check itself, would likely result
   in overflow, not underflow.

   Whether or not underflow is a quality issue depends on the needs of
   the application.

   If you loose $ 10E-23 due to a underflow, is that a problem?  What
   if you loose $ 10E-23 in each of 10E23 transactions?  How many
   customers over how many years does that come out to be?

   (No, I don't think 10E-23 is the right number, good enough for
    argument's sake.  You can work it out for whatever floating
    point format you're using.)

   If you're not processing money, the argument still applies.  For
   example, if you loose such a small amount every time you locate a
   bolt in a building design, could you possibly have enough bolts in
   a row to prevent the building from going together correctly?

   I've dealt with applications where the designer insisted that we
   do all arithmetic in double precision floating point, even though
   the result was stored in a 16 bit integer, and there was no noticable
   affect of a result off by less than .01% .  I can't imagine underflow 
   being an issue in that one.